(1) Field of the Invention
As is known, there are already road vehicles, in particular motor vehicles, using hybrid drive assemblies, i.e. vehicles in which an internal combustion engine and an electric motor are used in combination with each other.
(2) Description of Related Art
The known hybrid solutions allow the alternative or combined use of the two propulsion systems: according to a first known combined configuration, called “hybrid series”, the internal combustion engine has the sole function of entraining an electric current generator, which recharges the batteries which charge the electric motor; the propulsion is therefore exclusively effected by the electric motor.
This solution offers the advantage of substantially reducing the consumptions as the internal combustion engine only has to supply the average power and can therefore function under stationary and optimized conditions.
In a second configuration, known as the “hybrid parallel” configuration, both internal combustion and electric engines are connected at the driving wheels through specific transmission kinematic mechanisms.
The known hybrid drive assemblies have the disadvantage of having complex structures, being costly and require a high encumbrance, with the result that there are only a few applications of this type of hybrid system on motor-vehicles having reduced dimensions such as scooters.
In particular, Italian patent application TO2002A001088 describes a hybrid drive assembly for scooters which uses an electric machine coaxial to the centrifugal clutch of the transmission unit interposed between the drive shaft of the internal combustion engine and transmission shaft. In this case, the rotor of the electric machine is integral with the clutch bell.
The known hybrid drive assembly for scooters is operated according to a method which comprises the following operative modes:                “thermal”, in which the propulsion is exclusively supplied by the internal combustion engine;        “electric”, in which the propulsion is exclusively supplied by the electric machine;        “hybrid parallel”, in which the internal combustion engine and the electric motor contribute to supplying the driving power; and        “hybrid series”, in which the internal combustion engine is exclusively used for the entrainment of an electric generator for recharging the batteries, whereas the propeller torque to the driving wheel is supplied by the electric machine alone.        
The combined operative modes currently known for the piloting of a hybrid drive assembly for scooters are not capable of optimizing the energy consumption of the vehicle and guaranteeing a charge level of the batteries at a predefined value. They only envisage, in fact, the possibility of supplying the torques of both engines to the driving wheel or charging the batteries through the internal combustion engine whereas the electric motor supplies the torque required.
In this latter case, the use of a specific current generator is also necessary, as the electric machine is engaged in acting as a motor and it is therefore not possible to exploit its reversibility characteristic.
What the present invention proposes to undertake is to eliminate the disadvantages reported above in known types of methods for managing the functioning modes of hybrid drive assemblys, by conceiving a method which is capable of guaranteeing a high functioning performance in terms of optimization of the energy control.